If still unsuccessful, I suggest contacting Telus directly, or making payment through your online banking interface.
If you find a post useful, please give the author a "Like"
I have this exact same problem. After clicking on "Pay Bill". the message "something went wrong...." appears. I have tried two different browsers on my desktop computer and on my phone...always get this message. Therefore can't pay online. In Telus chat, communicating with a real person for another issue, I mentioned this. They did not seem aware of the problem, suggested different browsers, but as I said that did not work. Very inconvenient.